Transmission systems are used in a wide variety of vehicles to transmit power generated by an engine or motor to torque at the vehicle's axle and wheels. Transmissions often include combinations of differently-sized gears to provide varied or shiftable gear ratios, which reflect the relationship between the turning speed of the axle and the turning speed of the shaft of the motor. Depending on the nature of the motor, the motor's power or efficiency may vary over the range of possible turning speeds. Variable speed transmissions with shiftable gear ratios enable the vehicle to realize optimal motor power over a broader range of axle speeds, and thus vehicle speeds, than is possible when only a single gear ratio is available.
In the design of miniature, remote radio frequency controlled vehicles used by children and hobbyists, a variable speed transmission is desirable in order to increase the range of speeds at which the vehicle may be operated. However, in most cases a primary goal is to reduce cost and complexity in the design of such vehicles without sacrificing utility. We have found that a two-speed transmission having a low gear and a high gear works well in toy cars and other such vehicles. The gear ratio for low gear is selected to enable the vehicle to climb grades, obstacles and rough terrain at low speed and under substantially peak motor power. The gear ratio for high gear is selected to enable the vehicle to reach high speeds at a relatively low motor revolution rate.
The present invention provides a method and apparatus for shifting a transmission between high and low gear modes and locking the transmission in either mode.